- Sep 13, 2001
The first time you saw extruded feed, you probably thought, "Ick. Dog food!" The nondescript brown lumps do look a lot like your hound's kibble, or some sort of uninspired version of Cocoa Puffs, and in fact they're made by the same process--but as horse feeds go, they're actually quite unique. Those puffed-up nuggets of grain can slow down your horse's rate of feed intake and reduce the risk of choke and colic, and their superior digestibility can help horses extract more energy from less feed.
Extrusion--a process of cooking ground grains with pressure and moist heat, then exposing them to cooler air so they "pop" like a kernel of corn--has been used for decades in the pet food industry, as well as for human edibles like breakfast cereals and corn chips. However, it wasn't until the 1980s that it was used to make horse feed. Even then, it was slow to catch on; horse people were a little suspicious of the unfamiliar format, and some horses were, too. Today, extruded feeds have a significant share of the market, a convincing indication of their value in many feed programs.
In The Mill
Unlike pelleted feeds, which are warmed with dry heat for a brief period, then pushed through a die (a large plate with holes in it, which forms the pellet shapes), extruded feeds actually are cooked at a temperature ranging upwards of 260°F. The grains first are ground, then placed in a sealed barrel called a conditioner, where hot steam and pressure make several changes in their composition. Most importantly, the heat softens the mixture and breaks the cross-links in the crystalline structure of the grain's starches, gelatinizing them just as enzymes would do in the horse's digestive system. The result is that the energy in the starches is made more available for absorption in the small intestine (the site where most digestion of concentrates occurs).
In essence, the cooking process "pre-digests" the starches so the horse's gut has to do less work. Not every horse needs this kind of help, of course, but for many, it's a significant plus. (Two other methods of feed processing--micronizing, which is cooking with dry heat, and steaming, which uses wet heat--also partially gelatinizes grain starches, but neither does as thorough a job as extrusion's heat plus pressure.)
The cooking process takes about 10 minutes, according to Al Kennedy, DVM, who worked for 18 years as the quality assurance manager for Martin's Feeds, a Canadian manufacturer of extruded rations for horses, pets, poultry, and fish. Along the way, the starches become more soluble in water (which also enhances digestion), and protein molecules are ruptured. "Not down to the amino acid level," Kennedy notes, "but enough to improve their absorption."
One of the pluses of the extrusion process is that it's very easy to add ingredients to the mix and to have them be incorporated into the final pellet. Fats, in the form of vegetable oils, often are included in formulas for extruded feeds, both to enhance digestion further and to give a shine to the horse's coat. Kennedy notes that there is a limit to the amount of fat that can be added before cooking, however. "Past a certain level, the oil interferes with the extrusion process and limits the expansion of the pellets," he says.
Manufacturers have discovered a way around this for pet foods, which often have a fat level of 18% to 20%: "You can add fat by spraying hot oil on the drying pellets," says Kennedy. "Because the pellets are porous, the oil sinks in." This method can be used for high-fat horse feeds designed for maximum performance.
Something usually not added to extruded feeds are preservatives. Because the eventual moisture content of the feed is so low, preservatives generally aren't needed. If one is used in the formula, it usually is there to keep the added fats from becoming rancid, and it's often a natural anti-oxidant such as vitamin E or vitamin C.
Cooking grains with moist heat does have a down-side, of course--it tends to destroy some of the grain's natural vitamin content (estimates are that between 5% and 40% of vitamin activity is lost, depending on the processing temperature and the cooking time). To compensate for this, most feed companies add higher amounts of the vulnerable vitamins to the mix before heat is applied; this way, even with some of the vitamins deactivated, the overall nutrient content of the feed still will be satisfactory at the end.
There's no deterioration of minerals, according to Kennedy.
Once all of the ingredients are well-softened by the cooking process, making a mass that's almost doughy in quality, it's time to make kibble. To do this, the mixture is forced through an extruder--essentially a large steel tube with an auger (a "screw" that rotates and increases pressure on the mixture). More steam and water are added at this point. Eventually the dough reaches a die plate with cone-shaped holes in it. The feed enters at the smaller end of the holes, and expands as it's forced through, emerging at the larger end. "It comes out like spaghetti," Kennedy explains, "and revolving knives cut off the nuggets at a certain size, which can be varied depending on what you're making." (Although horse feed manufacturers haven't gotten very creative with their dies, it's interesting to note that it's possible to create any number of interesting shapes depending on the shape of the holes in the die plate. Many pet food manufacturers take advantage of this to create their own unique "look" for their products.) The higher the temperature of the cooking process, the more the nuggets expand on encountering the cooler, drier air of the feed mill.
Once the expansion is complete, the extruded feed is placed on a drying belt to complete the process. When it first emerges from the extruder, the feed will contain about 30% moisture--but it will need to have less than 10% moisture to be ready for bagging. (Otherwise, says Kennedy, mold is a real possibility.) The drying belt is a wide metal belt riddled with little perforations. As the feed is carried along its length (about 20 to 30 feet), hot air is blown on the belt from below, drying the feed and encouraging it to harden into the crunchy nuggets with which we're familiar. During this time, samples are taken to check for moisture, density, and nutrient content to ensure every batch is consistent.
"You want to see good conversion of the starches, an indicator that the cooking was thorough," Kennedy says. "In horse feeds, the ideal is over 85% (starch) conversion. That's not usually difficult to achieve, because horse feeds, being all-vegetable, cook more thoroughly and expand better than pet foods with animal products like fish or poultry meal in them."
Finally, the feed is bagged and prepared for shipping to your feed store. The whole process takes about three hours, on average.
Why Extruded Feed?
Extruded feeds have several significant advantages over their more traditional counterparts, sweet feeds and pellets. First, because the extrusion process creates a feed that is about twice as large and half as dense as a "loose" grain mix or pellet made with the same ingredients, it takes most horses longer to eat it. Studies have indicated that horses eating extruded rations take between 22% and 32% longer to eat their grain (and it might take them even longer when they're first getting accustomed to the feed).
Slower eating means: 1) That horses have more "chew time," which can help satisfy their grazing urge and discourage them from snacking on the barn and fences, and 2) They'll be less likely to bolt their food and put themselves at risk for choke and colic.
So, extruded feeds are a particularly good choice for a Type A personality who inhales his grain rather than savoring it.
It's suspected--although it's difficult to measure this directly--that horses which eat extruded feeds retain more water in their cecums (the fiber-fermenting "vat" in the large intestine), which can reduce the risk of impaction colic and help prevent dehydration in stressful situations such as long-distance trailering.
Probably most important is there's good evidence that the overall digestibility of extruded feeds is higher than that of plain grains, sweet feeds, or pellets. In one study at the University of Florida in the 1980s, weanlings fed extruded feeds grew faster and showed 18.5% better feed efficiency than weanlings on a pelleted feed that contained the same ingredients. It's believed that the better feed efficiency is a result of extruded feeds being more completely digested in the small intestine, rather than in the cecum. Most nutritionists believe that the process of gelatinizing the starches improves their utilization, as it's been proven to do in other species (including dogs, cats, pigs, and poultry)--although there have been a few conflicting studies that suggest it doesn't provide as dramatic an advantage in horses and cattle.
However that increased feed utilization is reached, it has a major advantage--it has been demonstrated to reduce significantly the incidence of digestive disturbances, otherwise known as colic. So, if you have a horse who's colic-prone, it might be to his benefit to switch from a sweet feed or pelleted ration to an extruded feed.
"Hard keepers" and geriatric horses are two other groups that can benefit from the increased nutrient availability of an extruded diet.
In addition, because of the longer chew time and better utilization of extruded feeds, many owners find they can feed less and get the same benefits--sometimes up to 20% less feed by weight. And because extruded feeds are, in a sense, "pre-digested," they often are recommended for horses which have such high energy needs that they require grain to be more than 50% of their overall diets (mostly young horses in intense race training).
The idea here is that if you're going to provide a large quantity of concentrated energy, you should at least assist the horse in processing and absorbing that fuel in the small intestine, where it can be fully utilized, rather than have it swept along, half-digested, to the cecum (where fermentative digestion of the material can cause serious gastrointestinal upset).
Finally, extruded feeds tend to be very low in dust and fines, which is always good news for the equine respiratory tract. They have a long shelf life, ranging up to a year (unless exposed to moisture). Because the nuggets are hard rather than crumbly, it's almost impossible for horses to sort out ingredients. They even can be soaked in water to make a softer meal for a horse with dental problems. So all in all, extruded feeds have a lot going for them.
A Few Cons Among The Pros
So what's the down-side? Well, the most significant one is that extruded feeds are expensive. Because the manufacturing process requires specialized equipment and close monitoring, extruded feeds are almost always pricier than comparable sweet feeds and pelleted rations.
Second, because the nuggets are only half as dense as unprocessed grains, they tend to take up a lot of room, and that can create a storage problem for some people. Do some comparing at your feed store and you'll quickly notice how large, yet how light, an average bag of extruded feed is. If you've got lots of room in your barn, it's not an issue; but if you're pressed for space, it's something to consider.
Third, like pelleted feeds, extruded "nuggets" are pretty homogenized--you can't examine the individual ingredients for freshness and quality the way you can the grains in a sweet feed. You'll have to trust the reputation and the warranties of your manufacturer.
Palatability probably is the biggest issue horses--and horse owners--have with extruded feeds. Perhaps it's the unfamiliar shape and texture, rather than the smell, but many equines find extruded nuggets something of an acquired taste. Most eventually do learn to accept the format, but particularly fussy eaters might be difficult to persuade--even though some feed companies attempt to make the kibble more attractive by coating them with molasses. If you're planning to switch to an extruded feed, make sure you do so gradually, over a period of weeks rather than days, to give your horse plenty of time to adjust.
A Couple Of Reassurances
People tend to be suspicious of the new and different, and extruded feeds were no exception when they were introduced. A couple of myths about this feed format persist, and we might as well expose them here:
1) There is no truth to the idea that extruded feeds can swell in the gut and cause colic or gastric rupture. If you soak extruded nuggets in water, you'll notice that while they soften, they don't increase significantly in size.
2) There is no difference in the rate of fermentation digestion between processed (ground) feeds and unprocessed grain mixes (i.e. sweet feed)--at least in non-geriatric horses with good dentition. So there's no truth to the notion that finely ground grains are more rapidly absorbed and cause excess gas production in the gut (leading to spasmodic colic). They're just more thoroughly absorbed.
Whether you decide to incorporate an extruded feed in your horse's diet is up to you--but don't be put off just because it looks like dog kibble. You might be missing out on a feed that can be a real problem-solver.
About the Author
Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.
POLL: University Equine Hospitals